The invention relates to a circular knitting machine for the production of goods with enmeshed fibers, having a needle cylinder providing support for knitting tools, at least one comb for combing the fibers into the needles, an exhaust hood surmounting the needle cylinder and serving for the aspiration and removal of loose fibers, and at least one component disposed inside or outside of the exhaust hood and fastened to the latter by means of at least one strut.
In known circular knitting machines of this kind (U.S. Pat. Nos. 3,014,355 and 3,968,662, and German OS No. 2,307,111), the component consists of a base plate largely covering over the bottom intake opening, a second exhaust hood disposed inside of and below a first air exhaust hood for the aspiration of loose fibers from the surface of the knit goods and from within the needle cylinder, or it consists of air guiding means which are intended both to improve the enmeshing action and to reduce fiber losses. The component is fastened to the exhaust hood in each case by means of struts. These constitute obstacles in the exhaust stream, on which loose fibers rapidly accumulate, form clumps, and reduce the airflow cross section, and this requires frequent maintenance operations. This effect is worsened by the amounts of oil and water (needle oil, condensation water or the like) produced in the operation of the circular knitting machine, which greatly promote the adherence of the loose fibers to the struts. Aside from the rapid contamination of the struts the above-mentioned, known exhaust hoods are characterized by a low aspirating efficiency or else by a high consumption of energy.
For the avoidance of this disadvantage in another known circular knitting machine (German OS No. 2,633,912), an air guiding means disposed below or within the exhaust hood is fastened to a shaft which is disposed coaxially in the needle cylinder and joined to that latter, so that it revolves with the needle cylinder. As a result of this arrangement, the knit goods have to be cut open lengthwise, and this is frequently undesirable.
Furthermore, in practice nowadays, only simple, truncated cone shaped or conical exhaust hoods are used. One consequence of this is low exhaust efficiencies, because the truncated cone shaped or conical exhaust hoods have their largest cross section, and hence their lowest aspirating power, at the point where the loose fibers are to be picked up and carried away.
Due to the low efficiency of the known exhaust apparatus, it is furthermore necessary to provide at each knitting station at least one air jet for the purpose of holding the fibers securely in the hooks of the knitting needles during the combing-in action and before the looping action. These air jets, in conjunction with the air movements produced by the needle cylinder rotation, result in considerable turbulence and air eddies which still further reduce the efficiency of the exhaust apparatus and often blow fibers which have already been inserted into the knitting needles back out of them before they have been bound into the basic goods, and this increases the fiber losses.
It is the object of the invention to increase the air-moving efficiency of the circular knitting machine described in the beginning, while reducing power consumption and fiber loss, and particularly to substantially eliminate the danger of the accumulation of loose fibers on the struts.